The partitioning error handling code was looking at
thd->lex->alter_info.partition_flags in non-alter-table cases, in which cases
the value is stale and contains whatever was set by any earlier ALTER TABLE.
This could cause the wrong error code to be generated, which then in some cases
can cause replication to break with "different errorcode" error.
Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>